1. Field of the Invention
The present invention relates generally to voltage regulators.
2. Description of the Related Art
A voltage regulator is an electrical regulator designed to automatically maintain an output voltage at a desired constant level. Electronic voltage regulators generally operate by comparing the present output voltage to some internal fixed reference voltage in a negative feedback control loop. The difference is then used to reduce the error between the present voltage and the desired voltage.
There are at least two broad types of voltage regulators. Switching regulators rapidly switch a series device on and off. These regulators are highly efficient because the switching element is either on or off so that it dissipates very little power. In contrast, linear regulators are constructed around devices that operate in their linear region. Although linear regulators provide a low-noise output signal, they are typically less efficient than switching regulators.
Linear voltage regulators always require the output voltage to be less than the input voltage. The difference between the input and the output voltages at which the circuit can no longer regulate the output voltage is referred to as the dropout voltage. A low-dropout (LDO) linear regulator is one which can operate with a very small dropout voltage.
Die area of a regulator is the area of an integrated circuit chip required by that regulator. Because die area is always a limited resource, an area-efficient voltage regulator is a valuable asset.